1. Field of the Invention
The present invention relates generally to a data storage/access network system for zooming image, more specifically to a data reading method and apparatus, a network system, an image zooming method and apparatus, an image data storage method and apparatus, an image data writing/reading system, and a recording medium.
2. Background of the Invention
Conventionally, many apparatuses each capable of storing digital image data in a memory or the like, reading out the image data, and displaying the image data are used.
Image data to be stored is input using an image input device such as an image scanner or a video camera using, e.g., a CCD. Most apparatuses can store a plurality of image data.
Individual image data are basically stored as image files. To store an image file having a large quantity of data, a large-capacity magnetooptical disk (MO) or hard disk (HDD) is used as a file storage unit. When an MO is used, one image data file is normally recorded on one MO. However, when the amount of image data constituting one image file exceeds the capacity of one MO, the image data is divided and stored in a plurality of MOs.
When the size of each image file is very large, as described above, or when a lot of image files are to be stored, a client/server system is implemented with a plurality of devices to store/read/display the image files via a network. More specifically, a plurality of image files are stored in a server. An image file designated from a client is read out and displayed on the display screen of the client.
When a large-scale image file unit is to be constituted using MOs on the server side, a disk library unit such as a jukebox capable of exchanging the plurality of MOs by an auto-change mechanism is used. In this disk library unit, disks are exchanged in accordance with an instruction from the client, so that a required image file is read out.
In the system of this type, since the size of each image file stored in the server is very large, the entire image data cannot be displayed in one screen because of the limited size of the display screen on the client side. Conventionally, image data stored in the server is reduced to a size which can be displayed in one screen, and displayed. For this reason, on the display screen of the client, the image cannot be displayed at the original precision.
When a detail of a photographic image is to be checked, or a specific component portion of a drawing is to be referred to in detail, the reduced entire image cannot cope with such a request. Therefore, part of the image must be enlarged to the full size of the screen and displayed at the original precision. According to this technique, when the entire image is to be observed, the image can be reduced and displayed, and when a detail is to be observed, the corresponding portion can be enlarged and displayed.
However, as described above, one image data is stored as one or a plurality of image files, and the image data is read out in units of files. For this reason, when a portion of the image is to be enlarged, the entire image file corresponding to the image data including the portion is transferred from the server to the client.
As described above, since each image file has a very large data amount, a long time is required for data transfer. Consequently, a long time is required after an enlargement/reduction instruction is issued from the client until the image is actually displayed. Especially when the network connecting the server to the client has a low transfer rate (when a personal computer is used as a client machine, the network inherently supported by a personal computer often has a low transfer rate), a very long time is required.
Even after file transfer, to display a detailed part of the entire image data which has been transferred in units of files, the entire image data must be temporarily developed on a memory, and only necessary image data must be extracted therefrom. This requires a large capacity of a work memory, and also a long time for extraction processing.
In addition, in the apparatus of this type using a disk library unit for storing image files, disk exchange for file read access takes a long processing time regardless of whether a detail is to be enlarged. For this reason, the time required after an image read instruction is issued until the image is actually displayed is prolonged. Particularly, when disk exchange is frequently performed in response to random access requests, the processing time until image display is greatly prolonged.
In this case, the display screen does not change during processing after an image zooming instruction is issued from the client. When the zoomed image is generated as instructed, the displayed image is switched to the zoomed image. For this reason, the user sometimes forgets the zooming target portion during the long-time zooming processing after the zooming instruction is issued. In addition, since no change is observed on the screen during the zooming processing, the user waiting for the processing may become irritated.
These problems are not limited to the above-described client/server system. An apparatus which performs digital signal processing for image data stored in one unit to zoom in or out the image is also proposed. However, in the apparatus of this type, digital processing for zooming takes a long time. For this reason, during processing after the zooming instruction is issued, the user may sometimes forget the zooming target portion or become irritated.
To perform the above processing of enlarging a detail of the image at a high speed, an image file storing detailed image data may be prepared in advance. However, portions that the user requests to enlarge are finite, and it is not practical to predict all such portions and store image files thereof. Because of the limited storage capacity, portions which can be enlarged are undesirably typified.
In the system or apparatus of this type, one image data is required to be displayed at various resolutions. For example, in addition to reduction of the entire image, a plurality of low-resolution reduced image information corresponding to original image data are simultaneously displayed on the screen as list icons such that a desired one of a plurality of stored image files can be easily found. There is also a requirement for displaying a coarse image for layout to cope with works in design industries or the like.
To deal with the requirement for displaying one image data at various resolutions, image data having various resolutions may be prepared in advance and stored independently of the original image file. With this method, since image data having various resolutions are prepared in advance, display processing can be performed at a relatively high speed. However, the amount of image data to be stored becomes enormous, resulting in an overall increase in storage capacity of the apparatus.
It is the first object of the present invention to perform processing of zooming an arbitrary portion in an entire image and displaying the image at an original precision at a high speed without increasing the storage capacity.
It is the second object of the present invention to clarify the zooming target portion of an image and reduce the stress of the user during zooming processing.
It is the third object of the present invention to allow processing of displaying one image data at various resolutions without increasing the entire storage capacity.
It is the fourth object of the present invention to allow processing of displaying one image data at various resolutions at a high speed without increasing the entire storage capacity.
It is the fifth object of the present invention to increase the rate for reading out data from a low-speed secondary storage unit such as a disk library unit which requires disk exchange.
It is the sixth object of the present invention to apply a means for speeding up the data read from the low-speed secondary storage unit independently of an application program.
According to an aspect of the present invention, there is provided a data reading method applied to a network system in which an image data storage device and an access device are connected, comprising steps of designating an arbitrary portion of image data displayed on the access device, reading out only the arbitrary portion designated as the access device from image data stored in the storage device in response to a request from the access device, and transferring the arbitrary portion to the access device through a network.
According to another aspect of the present invention, there is provided a data reading apparatus applied to a network system in which an image data storage device and an access device are connected, comprising interpretation means for interpreting a request signal sent from the access device, to know what region in image data stored in the access device is requested to be read out, and image read means for reading out only an arbitrary portion of image data stored in the storage device in accordance with an interpretation result from the interpretation means and transferring the arbitrary portion to the access device through a network.
According to still another aspect of the present invention, there is provided a network system in which an image data storage device and an access device are connected, the access device comprises region designation means for designating an arbitrary partial region of entire image data stored in the storage device, and request means for transferring the partial region designated by the region designation means to the storage device through a network as a request signal. The storage device comprises interpretation means for interpreting the request signal sent from the access device to know what region in image data stored in the access device is requested to be read out, and image read means for reading out image data in the designated partial region from the stored image data in accordance with an interpretation result from the interpretation means and transferring the read-out image data to the access device through the network.
According to the present invention having the above arrangements, when a request for using a partial region is issued on the image data access device side, only image data in the requested partial region is dynamically extracted on the image data storage device and transferred instead of transferring the entire file including the corresponding image data. With this processing, the amount of data to be transferred can be decreased. In addition, since the partial region of image data is dynamically extracted, all partial regions to be used need not be predicted, and image data in these regions need not be prepared and stored in advance.
According to still another aspect of the present invention, the image data access device in the network system further comprises image zooming means for, while the image read means in the storage device is reading/transferring the image data in the partial region, performing digital signal processing for image data which has already been stored in the access device, thereby sequentially displaying a plurality of steps of zoomed images generated by changing stepwise a zoom ratio of an image which is currently being displayed, and display is switched to the image data transferred by the image read means after the image is zoomed to a full size of a display screen of the access device.
According to this aspect of the present invention having the above arrangement, after enlargement of a partial region is instructed on the image data access device; until the enlarged image is displayed at the proper resolution, the process of gradually zooming the image in the partial region is displayed.
According to still another aspect of the present invention, there is provided a data reading method applied to a network system in which an image data storage device and an access device are connected, comprising steps of, when image data stored in the storage device is to be read out, performing conversion of the image data into image data having a resolution corresponding to a request from the access device, and transferring the converted image data to the access device through a network.
According to still another aspect of the present invention, there is provided a data reading apparatus applied to a network system in which an image data storage device and an access device are connected, comprising interpretation means for interpreting a request signal sent from the access device to know what resolution image data stored in the storage device is requested to be displayed at, and image read means for, when the image data stored in the storage device is to be read out, converting the image data into image data having a resolution corresponding to the request from the access device in accordance with an interpretation result from the interpretation means and transferring the converted image data to the access device through a network.
According to still another aspect of the present invention, there is provided a network system in which an image data storage device and an access device are connected. The access device comprises resolution designation means for designating a resolution to display an image at a desired resolution, and request means for transferring information designated by the resolution designation means to the storage device through a network as a request signal. The storage device comprises interpretation means for interpreting the request signal sent from the access device to know what resolution image data stored in the storage device is requested to be displayed at, and image read means for, when the image data stored in the storage device is to be read out, converting the image data into image data having a resolution corresponding to the request from the access device in accordance with an interpretation result from the interpretation means and transferring the converted image data to the access device through the network.
According to this aspect of the present invention having the above arrangement, when a request for displaying an image at a certain resolution is issued on the image data access device side, image data having the original resolution and stored in the storage device is dynamically resolution-converted on the storage device and then transferred to the access device. With this arrangement, an image can be displayed at various resolutions only by storing the image data having the original resolution without independently preparing and storing image data having various resolutions in advance.
According to still another aspect of the present invention, there is provided an image zooming method of zooming a displayed image by digital signal processing, comprising steps of repeatedly performing, in zooming in an image, processing of generating, from the image in a region as a zooming target, an image at a zoom ratio between a current zoom ratio and a final zoom ratio and displaying the image while changing the zoom ratio stepwise until the zoom ratio, and superimposing the image generated with changing the zoom ratio stepwise, on the original image before zooming.
According to still another aspect of the present invention, there is provided an image zooming method of zooming a displayed image by digital signal processing, comprising steps of repeatedly performing, in zooming out an image, processing of generating, from the image in a region as a zooming target, an image at a zoom ratio between a current zoom ratio and a final zoom ratio and displaying the image while changing the zoom ratio stepwise until the zoom ratio reaches the final zoom ratio, and, when the zoom ratio reaches the final zoom ratio, displaying the image zoomed out by the final zoom ratio in an entire display frame, including an image portion which has not been displayed before the zoom out reaches the final zoom ratio.
According to the present invention having the above arrangement, the original image can be prevented from being suddenly switched to the image at the final zoom ratio when a certain time has elapsed after the image zooming instruction is issued. Instead, the process of gradually zooming the target image to the final zoomed image is displayed. Therefore, the zooming target portion can be visually confirmed even during the zooming processing.
According to still another aspect of the present invention, there is provided an image data storage method of storing image data in a storage medium, comprising steps of dividing data on all scan lines constituting an original image, into a plurality of resolution components by considering data on each group of scan lines at equal intervals in the data on all scan lines constituting the original image to be one unit of resolution component data, and putting together the data on scan lines of each different width of the equal interval, rearranging the plurality of resolution component data such that data belonging to the same resolution component are put together and data of a lower resolution component with a wider width than the regular interval is stored in an upper layer of the storage area of the storage medium while data of a higher resolution component with a narrower width than the regular interval is stored in a lower layer of the storage area of the storage medium, and hierarchically storing the respective resolution component data in a storage area of the storage medium.
According to the present invention having the above arrangement, one original image data is divided into a plurality of resolution components and hierarchically stored in the storage medium in advance. Therefore, when a request for displaying an image at a certain resolution is issued, an image having the requested resolution can be obtained only by reading out the necessary resolution component for realizing the requested resolution without performing cumbersome resolution conversion processing.
According to still another aspect of the present invention, there is provided an image data storage method of storing image data in a storage medium, comprising steps of rearranging data of scan lines constituting an original image such that data belonging to the same resolution component are put together, and hierarchically storing the respective resolution component data in a storage area of the storage medium.
According to this aspect of the present invention having the above arrangement, data compression processing can be performed in units of scan lines, so that a high compression ratio can be achieved using the identity or similarity of pixel data present on the scan lines. In addition, data read processing can also be performed in units of scan lines. Therefore, even when a request for extracting an arbitrary portion in image data is issued, only corresponding scan line data need be read out and developed on the memory in extraction processing, so the entire image data need not be developed.
According to still another aspect of the present invention, in the image data storage method, lower-resolution component data is stored in an upper layer of the storage area of the storage medium, and higher-resolution component data is stored in a lower layer of the storage area of the storage medium.
According to this aspect of the present invention having the above arrangement, low-resolution component data whose use frequency is low is stored in an area with a smaller address number, and high-resolution component data whose use frequency is high is stored in an area with a larger address number. For this reason, each resolution component data can be more smoothly read out.
According to still another aspect of the present invention, in the image data storage method, the plurality of resolution component data divided from the original image data are stored in a plurality of storage media.
According to this aspect of the present invention having the above arrangement, high-resolution component data whose amount is large and use frequency is low can be stored in a large-capacity storage medium, and low-resolution component data whose amount is small and use frequency is high can be stored in a storage medium which allows high-speed read access. With this arrangement, even when all the resolution component data cannot be stored in a storage medium which allows high-speed access because of the limited data capacity, the rate for reading out at least data with a high use frequency can be increased.
According to still another aspect of the present invention, there is provided an image data writing/reading system comprising data division means for dividing data on all scan lines constituting an input original image, into a plurality of resolution components by considering data on each group of scan lines at equal intervals in the data on all scan lines constituting the original image to be one unit of resolution component data, and putting together the data on scan lines of each different width of the equal interval, data storage means for rearranging the plurality of resolution component data divided by the data division means such that data belonging to the same resolution component are put together, and hierarchically storing the respective resolution component data in a storage area of the storage medium, data read means for reading out only one of the respective resolution component data stored in the storage medium by the data storage means in correspondence with a request from a user, and image display means for displaying an image on the basis of the data read out by the data read means.
The data read means has prefetch means for, when a request for reading out data is issued, developing in advance another data associated as data which is likely to be read out next to the requested data in accordance with a predetermined rule from a storage medium whose read rate is low to a storage medium whose read rate is high.
According to the present invention having the above arrangement, even when a request for reading out certain data is actually issued for the first time, the corresponding data can be read out not from the low-speed storage medium but from the high-speed storage medium as far as the data has already been developed from the low-speed storage medium to the high-speed storage medium in preceding processing of reading out another data. Therefore, not only for data having a high use frequency but also for data having a relatively low use frequency, the read processing time can be substantially shortened.
According to still another aspect of the present invention, there is provided a data reading method comprising the steps of dividing data on all scan lines constituting an original image into a plurality of resolution components by considering data on each group of scan lines at equal intervals in the data on all scan lines constituting the original image to be one unit of resolution component data, putting together the data on scan lines of each different width of the equal interval, rearranging the plurality of resolution component data such that data belonging to the same resolution component are put together and data of a lower resolution component with a wider width than the regular interval is stored in an upper layer of the storage area of a storage medium while data of a higher resolution component with a narrower width than the regular interval is stored in a lower layer of the storage area of the storage medium, and developing in advance, when a request for reading out data of a low resolution component, is issued to the storage medium, another data of a higher resolution component associated as data which is likely to be read out next to the requested low resolution component data in accordance with a predetermined rule from a low-speed storage unit to a high-speed storage unit.
According to the present invention having the above arrangement, even when a request for reading out certain data is actually issued for the first time, the corresponding data can be read out not from the low-speed storage unit but from the high-speed storage unit as far as the data has already been developed from the low-speed storage unit to the high-speed storage unit in preceding processing of reading out another data. With this arrangement, the rate for reading out data from the low-speed storage unit can be substantially increased. Processing of developing data in advance is performed on the basis of the rule defined to associate the data as data which is likely to be read out next. For this reason, even in response to a read request issued for the first time, the high-speed storage unit can often be accessed to read out the data, so the data read processing time can be shortened as a whole.
Besides, according to the present invention, since each unit of original image data is beforehand divided into a plurality of resolution components and stored in the storage medium in a hierarchical structure, an image having a necessary resolution can be obtained only by reading out the necessary resolution component for realizing the necessary resolution without performing cumbersome resolution conversion processing.
According to still another aspect of the present invention, there is provided a data reading method of developing data in advance while causing an operating system applied to a computer to interpret the predetermined rule.
According to this aspect of the present invention having the above arrangement, processing of developing data from the low-speed storage unit to the high-speed storage unit is performed at the level of the operating system applied to the computer without mediacy of the application program. Therefore, the application program need not be modified to incorporate this function, and the function can be readily optionally incorporated in any application program.